Driveshaft Runout and Balancing
Driveshaft Runout and Balancing
Driveshaft Inspection
NOTE: Driveline vibration exhibits a higher frequency and lower amplitude than high-speed shake. Driveline vibration is directly related to the speed of the vehicle and is noticed at various speeds. Driveline vibration can be perceived as a tremor in the floorpan or heard as a rumble, hum or boom.
NOTE: Refer to Specifications for all runout specifications.
1. NOTE: Do not make any adjustments before carrying out a road test. Do not change the tire pressure or the vehicle load.
Carry out a visual inspection of the vehicle. Operate the vehicle and verify the condition by reproducing it during the road test.
^ The concern should be directly related to vehicle road speed, not affected by acceleration or deceleration, or could not be reduced by coasting in NEUTRAL.
2. With the vehicle in NEUTRAL, position it on a hoist. For additional information, refer to Maintenance/Service and Repair.
^ The driveshaft should be kept at an angle equal to or close to the curb weighted position. Use a twin-post hoist or a frame hoist with jackstands.
3. Inspect the driveshaft for damage, undercoating or incorrectly seated U-joints. Rotate the driveshaft slowly by hand and feel for binding or end play in the U-joint trunnions. Remove and inspect the slip yoke splines for any galling, dirt, rust or incorrect lubrication. Clean the driveshaft or install new U-joints as necessary. Install a new driveshaft if damaged. After any corrections or new components are installed, recheck for the vibration at the road test speed.
^ If the vibration is gone, test drive the vehicle.
^ If the vibration persists or the driveshaft passes visual inspection, measure the driveshaft runout.
Driveshaft Runout
1. Install a dial indicator. Rotate the driveshaft by turning the axle and measure the runout at the front, the center and the rear of the driveshaft.
^ If the runout exceeds specifications at the front or center, install a new driveshaft.
^ If the front and center is within specification, but the rear runout is not, index-mark the rear runout high point and proceed to Step 2.
^ If the runout is within specification at all points, recheck for vibration at road test speed. If the vibration persists, balance the driveshaft. Proceed to Driveshaft Balancing in this procedure.
2. NOTE: Circular pinion flanges can be turned in 90 degree or 1/4 increments. Half round pinion flanges are limited to 2 positions.
Index-mark the driveshaft to the pinion flange. Disconnect the driveshaft and rotate it 180 degrees. Reconnect the driveshaft. Recheck the runout at the rear of the driveshaft.
^ If the runout is still over specification, mark the high point and proceed to Step 3.
^ If the runout is within specification, check for the vibration at the road test speed. If the vibration is still present, balance the driveshaft. Proceed to Driveshaft Balancing in this procedure.
3. Excessive driveshaft runout can originate in the driveshaft itself or from the pinion flange. To find the source, compare the 2 high points previously determined.
^ If the index marks are close together, within 25 mm (1 inch), the driveshaft is eccentric. Install a new driveshaft.
^ If the marks are on opposite sides of the driveshaft, 180 degrees apart, the slip yoke or pinion flange is responsible. Check the pinion flange runout. If the pinion flange runout exceeds specifications, a bent pinion is indicated.
^ If the pinion flange and pinion runouts are within specifications, road test and check for the vibration at the road test speed. If the vibration persists, balance the driveshaft. Proceed to Driveshaft Balancing in this procedure.
